This proposal is designed to enhance the understanding of brainstem modulation of the autonomic nervous system. Results will have broad implications for the understanding of the relationship between stress and autonomic dysfunction, as well as normal autonomic and adrenal function. Specifically, this proposal will test the following hypotheses using electrophysiological and morphological techniques: 1. Pre-adrenal neurons in the nucleus tractus solitarius (NTS) receive direct afferent input from fibers of the solitary tract. 2. Pre-adrenal neurons in the NTS receive input from local circuit neurons independent of primary afferent stimulation. 3. Pre-adrenal neurons in the NTS are modulated by noradrenaline.